Publications

Enhancement-mode two-channel triple quantum dot from an undoped Si/Si_0.8Ge_0.2 quantum well hetero-structure

Studenikin, S.A.S.; Gaudreau, L.G.; Kataoka, K.K.; Austing, D.G.A.; Lu, Tzu-Ming L.; Luhman, Dwight R.; Bethke, Donald T.; Wanke, Michael W.; Lilly, Michael L.; Carroll, Malcolm; Sachrajda, A.S.S.

Here, we demonstrate coupled triple dot operation and charge sensing capability for the recently introduced quantum dot technology employing undoped Si/Si_0.8Ge_0.2 hetero-structures which also incorporate a single metal-gate layer to simplify fabrication. Si/SiGe hetero-structures with a Ge concentration of 20% rather than the more usual 30% typically encountered offer higher electron mobility. The devices consist of two in-plane parallel electron channels that host a double dot in one channel and a single dot in the other channel. In a device where the channels are sufficiently close a triple dot in a triangular configuration is induced leading to regions in the charge stability diagram where three charge-addition lines of different slope approach each other and anti-cross. In a device where the channels are further apart, the single dot charge-senses the double dot with relative change of ~2% in the sensor current.